Excessive alcohol use is the third-leading preventable cause of death in the U.S. with young adults ages 18-29 showing the highest rates of hazardous alcohol use. Community colleges serve over 12 million students, comprising 45% of all U.S. college students. Community college students (CCS) show rates of heavy alcohol use similar to students at traditional four-year residential (FYR) colleges, but CCS are at higher risk for negative consequences of heavy drinking, including physical and sexual assault, fatal injuries, and driving under the influence. Despite the large number of CCS and their level of risk, alcohol interventions for young adults have focused almost exclusively on students at FYR colleges. CCS differ from those at FYR colleges in several ways; CCS are more likely to have multiple roles and responsibilities (e.g., employment), drive more (to/from campus), live with family, and socialize off campus, and thus require intervention approaches tailored to their life circumstances. Community colleges are less likely to offer health services than FYR institutions and typically lack resources needed to implement alcohol interventions that are recommended for traditional college students, such as in-person motivational counseling. Approaches that can deliver effective alcohol harm reduction messages to CCS using a modality that is flexible, accessible, and tailored to their specific needs are urgently needed. This proposed FastTrack STTR (PAR-17-303) builds on our successful pilot in which we developed a text message (TxM)-delivered alcohol intervention for, and in collaboration with CCS. In Phase I, we will develop and iteratively test a smartphone application (app) incorporating our TxM program with additional features and functionality requested by students in our pilot trial (Aim 1.1). After obtaining user feedback (Aim 1.2) we will complete programming in both iOS and Android languages (Aim 1.3). To ensure that the College Alcohol Risk Education System (CARES) is well positioned to get into the community college marketplace, it is critical to demonstrate efficacy. Therefore, in Phase II, we will conduct an efficacy trial (Aim 2.1) of CARES compared to a competing alcohol education program that would be feasible for most community colleges to adopt, thus providing a real-world comparison with data suitable to support our efforts in future commercialization. We also seek to identify the types of individuals for whom CARES is more/less effective (Aim 2.2), and identify how it might be improved (Aim 2.3). With an increasing number of states making community college free to state residents, demand for services is likely to increase rapidly in coming years. With over 1,400 community college systems across the U.S., this seems an opportune moment to be targeting this market for health promotion products such as the CARES app.